This invention pertains to aldol reactions of organic carbonyl compounds and more particularly to their chemical control by the use of a surfactant co-catalyst for said aldol reactions.
L. Claisen reported the preparation of acetaldol from acetaldehyde and aqueous potassium cyanide in 1899. The extension of this experiment to base catalyzed reactions between electron-accepting reactants, such as aldehydes or ketones, and electron-donating components having an active methylene group has led to many industrial chemical syntheses. The aldols obtained can be used as such or as intermediates for further reaction. For example, they can be reduced or dehydrated for use in other syntheses. Thus n-butyraldehyde has been used to make 2-ethylhexanol-1,2-ethylhexanediol (an insect repellant), and 2-ethylbutyric acid.
As with any commercial process there is a continuing demand to improve the economics of each step by increasing yields and increasing reaction rates. The process variables are further complicated when mixtures of carbonyl substrates are used. For example, a mixture of acetaldehyde and butyraldehyde is condensed and dehydrated to produce 2-ethylcrotonal, an intermediate for the synthesis of plasticizers. Since acetaldehyde and butyraldehyde also can undergo self-condensation by themselves, a number of competing reactions takes place leading to the uneconomical diversion of the reactants to undesired products, including 2-hexenal, crotonal, ethylpropylacrolein, and other oligomers plus polymers(rather than dimers). Similar product spreads are obtained when mixed ketones or aldehydes with ketones are subjected to aldol reaction conditions.
It is therefore an object of this invention to provide a means for chemically controlling the reactivities of organic carbonyl compounds in base-catalyzed condensations in order to enhance the yields of desired aldol reaction products and inhibit the formation of by-products, including resins.
It is another object of this invention to increase the reaction rates of the desired reaction paths.
It is still another object to reduce the energy requirements of aldol reactions by operating at lower temperatures than those conventionally in use.
It is still another object to employ co-catalyst surfactants which do not chemically react with the products of the aldol reaction.